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Figure 5.
Figure 5. (a) Molecular model of the PsTI/trypsin/chymotrypsin ternary complex showing the independent and
non-interacting trypsin and chymotrypsin sites. This model is consistent with simultaneous binding of the two pro-
teases. The PsTI molecule is shown in a green ribbon diagram, the molecular surfaces (calculated with the pro-
gramme GRASP) of trypsin and chymotrypsin are in yellow and blue, respectively. (b) Main interactions between
PsTI and trypsin. Hydrogen bonds are represented with broken lines. PsTI is in black and trypsin in white. (c) View
showing the complementarity between the phenyl ring of Tyr43 and the S1 pocket of chymotrypsin. The alpha-car-
bon trace of PsTI as well as all atoms of residue Tyr43, are shown in green. Residues of chymotrypsin which under-
line the pocket are in light blue. The S1 pocket of chymotrypsin is represented as a transparent surface. This
illustration was prepared using the programmes MOLSCRIPT, GRASP and RASTER3D (Merritt & Murphy, 1994).
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